diff options
| -rw-r--r-- | arch/x86/include/asm/i387.h | 42 | ||||
| -rw-r--r-- | arch/x86/kernel/traps.c | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/xsave.c | 10 |
3 files changed, 45 insertions, 8 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index 727c1dd84899..f704be239883 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -400,6 +400,48 @@ static inline void irq_ts_restore(int TS_state) } /* + * The question "does this thread have fpu access?" + * is slightly racy, since preemption could come in + * and revoke it immediately after the test. + * + * However, even in that very unlikely scenario, + * we can just assume we have FPU access - typically + * to save the FP state - we'll just take a #NM + * fault and get the FPU access back. + * + * The actual user_fpu_begin/end() functions + * need to be preemption-safe, though. + * + * NOTE! user_fpu_end() must be used only after you + * have saved the FP state, and user_fpu_begin() must + * be used only immediately before restoring it. + * These functions do not do any save/restore on + * their own. + */ +static inline int user_has_fpu(void) +{ + return current_thread_info()->status & TS_USEDFPU; +} + +static inline void user_fpu_end(void) +{ + preempt_disable(); + current_thread_info()->status &= ~TS_USEDFPU; + stts(); + preempt_enable(); +} + +static inline void user_fpu_begin(void) +{ + preempt_disable(); + if (!user_has_fpu()) { + clts(); + current_thread_info()->status |= TS_USEDFPU; + } + preempt_enable(); +} + +/* * These disable preemption on their own and are safe */ static inline void save_init_fpu(struct task_struct *tsk) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 8ba27dbc107a..982433b5da30 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -631,7 +631,6 @@ EXPORT_SYMBOL_GPL(math_state_restore); dotraplinkage void __kprobes do_device_not_available(struct pt_regs *regs, long error_code) { - WARN_ON_ONCE(!user_mode_vm(regs)); #ifdef CONFIG_MATH_EMULATION if (read_cr0() & X86_CR0_EM) { struct math_emu_info info = { }; diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index a3911343976b..86f1f09a738a 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -168,7 +168,7 @@ int save_i387_xstate(void __user *buf) if (!used_math()) return 0; - if (task_thread_info(tsk)->status & TS_USEDFPU) { + if (user_has_fpu()) { if (use_xsave()) err = xsave_user(buf); else @@ -176,8 +176,7 @@ int save_i387_xstate(void __user *buf) if (err) return err; - task_thread_info(tsk)->status &= ~TS_USEDFPU; - stts(); + user_fpu_end(); } else { sanitize_i387_state(tsk); if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave, @@ -292,10 +291,7 @@ int restore_i387_xstate(void __user *buf) return err; } - if (!(task_thread_info(current)->status & TS_USEDFPU)) { - clts(); - task_thread_info(current)->status |= TS_USEDFPU; - } + user_fpu_begin(); if (use_xsave()) err = restore_user_xstate(buf); else |